Often it becomes necessary to replace the existing ballast for a railroad track with fresh ballast such as when the old ballast becomes dirty or contaminated with foreign material or breaks down. Alternatively it may be necessary to remove the ballast in order to carry not necessary repairs to the track itself. Because of the network formed by the ties and rails of the track, it is difficult to remove such material with standard, commonly used earth or rock digging equipment.
Methods and machines have been proposed or used in the past which remove the ballast and other material from beneath the railroad ties, the machines sometimes being termed undercutters. Such machines generally employ a toothed chain which moves about an elongated horizontal chain track extending in a direction parallel to the ties of the track. The chain on the chain track is placed beneath the ties and as it operates it scarifies the ballast and pulls the ballast and any material mixed with it to one side of the bed of the railroad track. However present undercutter machines have proved unsatisfactory for track repair work in some areas and have a number of major disadvantages. First of all many undercutters presently in use can only be used where the railroad track and road bed are located above the surrounding ground level either by means of a ditch formed on each side of the track or by placing the roadbed on a built-up bank or ridge of suitable fill material. This limitation is due to the fact that the chain and chain track can only transport the ballast horizontally and therefore there must be an area beside the track into which one end of the chain means can extend and to which the chain means can transport the ballast.
Another problem with the prior art machines is that an unnecessarily large amount of the roadbed may have to be undercut in order for these machines to operate. For example, it may only be necessary to replace the ballast immediately between and underneath the ties of the track. The undercutter on the other hand will remove all the ballast from the side of the roadbed as well as the ballast around the ties because of the need for the undercutter to extend horizontally right out to the ditch or low area beside the roadbed. Thus considerable energy, time and material may be wasted.
In order for prior art undercutters to undercut track laid on a roadbed which is level with the surrounding ground and beside which there is no ditch, it may be necessary for a separate ditch digging machine to precede the undercutter and to form the necessary ditch alongside of the track. Alternatively it is necessary to provide means for transporting the ballast vertically from the delivery end of the chain means to a suitable location above the ground. In order to place the chain means beneath such a railroad track so that it can commence operation, a trench is dug alongside the track parallel thereto. In the past this has sometimes been done by difficult, time-consuming manual labour since it is not worthwhile to bring in a power digger just for this initial ditch. The chain means is then swung 90 degrees about a vertical axis to place it beneath the track.
Accordingly it is an object of the present invention to provide an apparatus and method for removing material from beneath railroad track which substantially overcomes the abovementioned disadvantages and problems with previously known undercutters.
It is another object of the apparatus of the present invention to provide suitable means for transporting ballast and other material delivered from beneath railroad track by horizontal chain means to a suitable location above the ground, the transporting means taking the form of rotary trench digging means. The apparatus is particularly suited for undercutting track at crossings, switches and weak spots which may form in the roadbed.
It is a further object of the present apparatus to provide suitable power means for digging an initial trench alongside of the track for the inseration of the horizontal chain means so that it can be swung to its operating position, the power means being the aforesaid trench digging means which also acts as the vertical transporting means.